Molecules and compounds were the topic of discussion when I popped into our school's science lab one day. A molecule is two or more atoms of an element chemically joined together. A compound, conversely, is when the two or more conjoined atoms are of different elements. Sodium chloride (NaCl), for example, would be a compound. Sodium and chloride combined form salt, salt being the whole or end result. Complementarity, two different elements fitting to complete a whole, is the spiritual principle at hand.
The Immaculate Conception of Mary can be understood according to the concept of complementarity. God's creation is meant to be whole (or holy). His creation is not a molecule. There are multiple elements. This is because of the fall of Adam and Eve, when mankind gave a resounding “No!” to God, which added the molecule of sin. God's creation, now existing as a compound, became negative. It was necessary to add an element of grace, or positivity—a pure and resounding “Yes!”—to complement the evil. This would be Mary. Mary's Immaculate Conception—the understanding that Mary is conceived without original sin from the very beginning of time—completes the picture of God's creation. God's compound is positive, since it consists of goodness added to the evil. Sin and grace are the complimentary elements.
If original sin and concupiscence seem to be ruling us, then we need an influx of Mary. When evil seems to be dominating our lives, praying to the Immaculate Conception will compliment us. We will never rid sin and evil from the world and from our lives, but we can continue to add grace through Mary to make our lives and our world a beautiful compound. Mary is the great chemist.